1. Field of the Invention
The present invention relates to methods for producing an electron-emitting device, an electron source comprised of a plurality of such electron-emitting devices, and an image-forming apparatus such as a display device or the like constructed using the electron source.
2. Related Background Art
The conventionally known electron-emitting devices are generally classified under two types, thermionic electron-emitting devices and cold-cathode electron-emitting devices. The cold-cathode electron-emitting devices include field emission type (hereinafter referred to as xe2x80x9cFE typexe2x80x9d) devices, metal/insulator/metal type (hereinafter referred to as xe2x80x9cMIM typexe2x80x9d) devices, surface electron-emitting devices, and so on.
Examples of FE type devices include those disclosed in W. P. Dyke and W. W. Dolan, xe2x80x9cField Emission,xe2x80x9d Advance in Electron Physics, 8, 89 (1956) or in C. A. Spindt, xe2x80x9cPhysical Properties of thin-film field emission cathodes with molybdenum cones,xe2x80x9d J. Appl. Phys., 47, 5248 (1976), and so on.
Examples of known MIM type devices include those disclosed in C. A. Mead, xe2x80x9cOperation of Tunnel-Emission Devices,xe2x80x9d J. Appl. Phys., 32, 646 (1961), and so on.
Examples of surface conduction electron-emitting devices include those disclosed in M. I. Elinson, Radio Eng. Electron Phys., 10, 1290 (1965), and so on.
Surface conduction electron-emitting devices utilize a phenomenon that electron emission occurs when electric current is allowed to flow in parallel to the surface in a thin film of a small area formed on an insulating substrate. Examples of surface conduction electron-emitting devices reported heretofore include those using a thin film of SnO2 by Elinson et al. cited above, those using a thin film of Au [G. Dittmer: xe2x80x9cThin Solid Films,xe2x80x9d 9, 317 (1972)], those using a thin film of In2O3/SnO2 [M. Hartwell and C. G. Fonstad: xe2x80x9cIEEE Trans. ED Conf.,xe2x80x9d 519, (1975)], those using a thin film of carbon [Hisashi Araki et al.: Shinku (Vacuum), Vol. 26, No. 1, p22 (1983)], and so on.
A typical example of these surface conduction electron-emitting devices is the device structure of M. Hartwell cited above, which is schematically shown in FIG. 18. In the same drawing, numeral 1 designates a substrate. Numeral 4 denotes an electrically conductive film, which is, for example, a thin film of a metallic oxide formed in an H-shaped pattern and in which an electron-emitting region 5 is formed by an energization operation called energization forming described hereinafter. In the drawing the gap L between the device electrodes is set to 0.5-1 mm and the width Wxe2x80x2 to 0.1 mm.
In these surface conduction electron-emitting devices, it was common practice to preliminarily subject the conductive film 4 to the energization operation called energization forming, prior to execution of electron emission, thereby forming the electron-emitting region 5. Specifically, the energization forming is an operation for applying a voltage to both ends of the conductive film 4 to locally break, deform, or modify the conductive film 4, thereby forming the electron-emitting region 5 in an electrically high resistance state. In the electron-emitting region 5 a fissure is formed in part of the conductive film 4 and electrons are emitted from near the fissure.
The surface conduction electron-emitting devices described above have an advantage of capability of forming an array of many devices across a large area, because of their simple structure. A variety of applications have been studied heretofore in order to take advantage of this feature. For example, they are applied to charged beam sources, and image-forming apparatus such as display devices and the like.
An example of a conventional application to formation of an array of many surface conduction electron-emitting devices is an electron source comprised of a lot of rows (in a ladder-like configuration), each row being formed by arraying the surface conduction electron-emitting devices in parallel and connecting both ends (both device electrodes) of the individual surface conduction electron-emitting devices by wires (common wires) (for example, see Japanese Laid-open Patent Applications No. 64-31332, No. 1-283749, and No. 2-257552).
Particularly, in the case of a display device, it can be formed as a plane type display device, similar to the display device made using a liquid crystal, and an example suggested as a self-emission type display device necessitating no back light is a display device comprised of a combination of an electron source consisting of a lot of surface conduction electron-emitting devices with a fluorescent member which emits visible light under irradiation with electron beams from the electron source (U.S. Pat. No. 5,066,883).
There are some conventional methods known as methods for producing the surface conduction electron-emitting devices described above. For example, a variety of methods, including vacuum vapor deposition, sputtering, chemical vapor deposition, dispersion coating, dipping coating, spinner coating, ink jet process (EP-A-0717428), and so on, are known as methods for forming the electroconductive film to be subjected to the above energization forming operation. The known energization forming methods on the electroconductive film include a method for energizing the electroconductive film while heating a substrate on which the electroconductive film is laid (Japanese Laid-open Patent Application No. 64-019658), a method for energizing the electroconductive film under a reducing ambience (Japanese Laid-open Patent Application No. 6-012997, EP-A-0732721), and so on.
In formation of the electroconductive film, it is desirable to form the film in uniform thickness in order to obtain good electron emission characteristics. There appear, however, differences in the uniformity, depending upon differences among the methods employed. Further, in the energization forming operation, particularly, where the forming operation of individual conductive films is carried out through wires to which the many conductive films are connected, thereby forming electron-emitting regions therein, it is desirable to perform such forming operation as to minimize variations in the electron emission characteristics among the individual conductive films. However, differences become greater in the variations of the characteristics as the number of electroconductive films connected increases.
An object of the present invention is to provide methods for producing an electron-emitting device capable of presenting good electron emission characteristics, an electron source incorporating such electron-emitting devices, and an image-forming apparatus.
Another object of the present invention is, particularly, to provide methods for producing an electron-emitting device capable of presenting good electron emission characteristics, independent of a method for forming its electroconductive film, an electron source incorporating such electron-emitting devices, and an image-forming apparatus.
Another object of the present invention is, particularly, to provide methods for producing an electron-emitting device capable of presenting good electron emission characteristics even with the energization operation on an electroconductive film having some thickness irregularities, an electron source incorporating such electron-emitting devices, and an image-forming apparatus.
Another object of the present invention is, particularly, to provide a method for producing an electron source having a plurality of electron-emitting devices with less variations in the electron emission characteristics.
Another object of the present invention is to provide a method for producing an image-forming apparatus capable of forming a higher-quality image.
For accomplishing the above objects, the present invention provides a method for producing an electron-emitting device comprising an electroconductive film having an electron-emitting region between electrodes, wherein a step of forming said electron-emitting region in the electroconductive film comprises a step of heating the electroconductive film and a step of energizing the electroconductive film, in an atmosphere in which a gas for promoting cohesion of the electroconductive film exists.
The present invention also provides a method for producing an electron-emitting device comprising an electroconductive film having an electron-emitting region between electrodes, wherein a step of forming said electron-emitting region in the electroconductive film comprises a step of energizing the electroconductive film while heating the electroconductive film, in an atmosphere in which a gas for promoting cohesion of the electroconductive film exists.
The present invention also provides a method for producing an electron source having a plurality of electron-emitting devices, wherein said electron-emitting devices are produced by either of the above-described methods for producing the electron-emitting device.
The present invention also provides a method for producing an image-forming apparatus comprising an electron source having a plurality of electron-emitting devices and an image-forming member for forming an image under irradiation of electrons from the electron source, wherein said electron-emitting devices are produced by either of the above-described methods for producing the electron-emitting device.